1. Technical Field
The present invention relates to an image reading apparatus, in particular, relates to a housing configuration of the image reading apparatus.
2. Related Art
There has been an existing scanner as an example of an image reading apparatus. The scanner is configured to read an image of a target through a glass plate by placing the target, for example, a document on a placement face (document table) of a transparent member (for example, glass plate) attached to a housing (case) and making an image reading unit such as a line sensor move (scan).
Accordingly, in order to read the image of the target accurately, the glass plate is required to be attached to the case firmly such that the target is not moved, that is, the glass plate on which the target is placed is not moved. As such attachment method, a method of attaching the glass plate to the case using an adhesive tape (double-stick adhesive tape) has been generally employed.
However, in an operation in which the glass plate is attached (fixed) to the case by the adhesive tape, for example, troublesome operations of bonding the adhesive tape to a specified position and peeling a protection tape are required. Further, when the glass plate or the like is damaged, the glass plate bonded by the adhesive tape is not easily peeled from the case. Therefore, in such case, the whole case is replaced in some case. This arises a problem that total manufacturing cost is increased. In order to solve the problem, a technique in which the glass plate is attached without using the adhesive tape has been proposed. For example, in JP-A-11-298685, a technique of attaching a glass plate to a case by biasing the glass plate in the direction (horizontal direction) along a placement face thereof using a biasing force by a biasing unit (coil spring or the like) has been disclosed.
However, in the attachment method described in JP-A-11-298685, the glass plate is inserted to and is engaged with a supporting portion located at the opposite side to the biasing unit. Therefore, the glass plate is required to be once slid in the direction against the biasing force by the biasing unit (that is, counter-insertion direction). To be more specific, the glass plate is required to be once slid by a predetermined amount corresponding to an engagement amount of the glass plate with the supporting portion along the insertion direction. Accordingly, the biasing force by the biasing unit is required to be set to such moving length that an operator who attaches the glass plate can slide the glass plate by a predetermined amount. Therefore, the biasing force by the biasing unit, which acts on the glass plate, cannot be made larger much in a state where the glass plate is inserted to and attached to the supporting portion. As a result, the biasing force acting on the attached glass plate, that is, a force of fixing the glass plate is not sufficient for practical use.